1. Field of the Invention
This invention relates to electronic circuits, and more particularly, to circuits for conveying selected ones of a number of different logic values.
2. Description of the Related Art
Selection circuitry is utilized in a wide variety of logic circuits in order to select one of a number of different logic values. One type of selection circuit is known as a multiplexer. A multiplexer may include a number of data inputs and a number of selection inputs. Based on a particular combination of selection inputs, a given one of the data inputs may be selected and provided as an output from the multiplexer. Various types of multiplexers configured to output a single bit of data may include a number of transistors arranged to form various logic gates, one of which may be used to output the selected data bit. Multi-bit multiplexers configured to select and output data sets made up of a number of bits (e.g., 8 bits) are also possible.
Selection circuits may also be used in memory applications to select memory cells in order to accomplish read operations. Within a given memory, selection circuits that are each coupled to a number of different cells of the memory may be coupled to various local bit lines. For a read operation, the bit lines may be precharged high. A decoder in the memory may receive address signals indicative of a memory address from which data is to be read. The decoder may generate word line signals based on the received address signals. These word line signals may be received by the selection circuitry within the memory, and may select the cell of the memory from which data is to be read. The selected cell may selectively discharge to the local bit line based on its stored value. If it is not discharged, a keeper circuit may hold the bit line high but may also impede the discharged of the selected cell by supplying current to resist the discharge.